Hot answers tagged

19

The human voice box produces a fundamental frequency and its harmonics because the mechanism is like that of a relaxation oscillator. However, we have limited control over the relative amplitude of the harmonics (we do have some - that is how we change the "color" of a tone we sing, and the sound of vowels). In order to produce the Shepard scale, you need ...


13

i've programmed some shepard tones and even a voice generator. The human voice can't make that sound for the same reason that a single or even 3 trumbones couldn't make it. if you had 12 trumbones you could conceivably put them on a wheel system so that the pitch of each is increased and when the top one reaches to top is muted and send down to the lowest ...


9

What we perceive as "sound" are (mechanical) oscillations of molecules from the source to the ear. This is for example why you cannot hear anything in vacuum, because there is no matter to oscillate. Light on the other hand is an electromagnetic wave. Therefore, there cannot be sound in our visual spectrum. It's in the wrong category. However, if you want ...


8

Playing a vinyl "LP" implies a 33 rpm motion and 30 cm diameter. The highest frequency recorded will depend on the track velocity and the size of the needle. 30 cm diameter implies a 100 cm track length (roughly - less as you move further in) traversed in about 2 seconds - or 50 cm / second. The radius of the needle is specified in the standard as less than ...


7

Wikipedia states that The high frequency response of vinyl depends on the cartridge. CD4 records contained frequencies up to 50 kHz, while some high-end turntable cartridges have frequency responses of 120 kHz while having flat frequency response over the audible band (e.g. 20 Hz to 15 kHz +/-0.3 dB).[5] In addition, frequencies of up to 122 kHz have ...


5

Sound could be considered a renewable resource if taken from a source that was created by continual physical processes - such as the sound of waves crashing against rocks. Although those sound waves contain energy (which is the kinetic energy of moving/vibrating air particles), their energy density is very low. Therefore they are not useful for generating ...


4

No, there is not. The eyes are receptors of electromagnetic waves and therefore they don't percipe sound. However, there are cases when you actually can see a sound effect on your own eyeballs, but they are unusual and a bit crazy. E.g. if you play low frequencies on a trombone and watch a screen with some repetition rate, then you can sometimes see an ...


4

I think you might be a little confused. The phrases 'renewable energy' and 'un-renewable energy' are used to refer to industrial sources of energy. These industrial sources include Wind, Solar, Wave, and Nuclear power, and traditional fossil fuels (coal, oil, natural gas etc.). If a source of power is renewable, it is not depleted (used up) when utilised ...


4

Acoustic levitation requires a material medium to transmit the sound waves that suspend the object you want suspended. The object must contact the medium in order to be suspended. If the object is made of antimatter, it will instantly annihilate upon contact with the material medium that transmits the acoustic waves. You can't transmit acoustic waves in ...


3

This is a common misconception. The function above can be interpreted as follows. Sound of frequency $\dfrac{\omega_1+\omega_2}{2}$ with amplitude modulated by the cos function of frequency $\dfrac{\omega_1-\omega_2}{2}$. The cosine function becomes zero twice every cycle as well as reaching a maximum magnitude twice every cycle. So the intensity of the ...


3

it has to do with the temperature lapse with altitude. since the speeed of sound is related to temperature by: $a = \sqrt{\gamma RT}$, where $\gamma$ and R are gas properties and T is temperature and the temperature profile follows (generally) like the left of these three plots: The area of interest for airliners is in the lowermost region where the ...


3

The basic phenomenon is that high frequency sound is more strongly attenuated than low frequency sound. The mechanism for sound attenuation is viscous damping. The absorption coefficient is $$ \gamma= \frac{\omega^2}{2\rho c^3}\left[ \frac{4}{3}\eta + \zeta + \kappa\left(\frac{1}{c_v}-\frac{1}{c_p}\right) \right], $$ where $\omega$ is the frequency, $\rho$ ...


3

A few observations. First - if you record sound for a short time, the bandwidth of the sample will result in a smearing of the peaks. This only really matters if the sample is very short - with a 1 second sample you would have 1 Hz resolution, but if you sample for 0.01 second, the bandwidth is 100 Hz. Second, you are using a scale that is quite compressed ...


3

A permanent magnet has a fixed north/south polarity - in this example, lets say north is facing up and south is facing down. This magnet has a membrane of some kind attached to its north face. An electromagnet beneath the permanent magnet can switch the direction of its north/south polarities by changing the direction of the electric current running ...


2

Thunder is a sonic boom, generated by the rapid heating of the atmosphere by the lightning discharge. The heat front moves faster than sound, generating the sonic boom. Thus what you hear is a pressure wave, and it can be carried by plasma, gas, liquid, or solid: by all of the states of matter.


2

Yes. Assuming that you have two independent and uncorrelated sound sources, then the intensity observed will be the sum of the intensity of the two sources. Whether they were summed electronically before being turned into sound, or whether they were generated as separate sound waves that are summed when they reach your ear, is irrelevant. Whether that ...


2

Sound waves are made of alternation of compression (higher density) and rarefaction (lower density) regions in the air. However, this can be somewhat difficult to visualize. Because of this, textbooks often show the wave like it's a string in the organ pipe. Really what the curves are showing you in the amplitude of this compression wave. It's also drawn ...


2

Based on the results, the pipe is clearly open at one end but closed on the other. Therefore $\lambda_n = \frac{(2n+1)L}{4}$ Your formalism is a bit unusual. If I can advise you, try to use something like this for harmonics: $$f_n=\frac{c}{\lambda_n} = and \ so \ on$$ Show explicitly the dependency on $n$.


2

You will get destructive interference when the difference in the distances from you to the two speakers is $n + \tfrac{1}{2}$ wavelengths. In your case that's 0.68m, 2.04m, 3.4m, and so on. You get constructive interference when the difference in the distances is an integral number of wavelengths. However the experiment is hard to do in a living room ...


2

There are three points to be noticed: If you just blow without closing the lips, you would change the boundary condition. The trumpet waveguide is not "nicely predictible", the approximation of an open tube does not work cause the bore variations $S(x)$. You need to solve this kind of beasts for reasonable 1D propagating pressure approximation: $$ ...


2

Yes. High intensity low frequency sound makes your eyeballs vibrate in your head, so you really can see (and feel) it. On a related topic, you can find the damped resonant frequency of your eyeballs by looking at the sweep line on an oscilloscope whose timebase has been set to around 50mS. If you then hit yourself downwards on the top of your head you will ...


2

Well, there is one simple thing you should do and that's doing that in right units: $$ p = A\sin (\omega t - kx) + B\sin(\omega t + kx) $$ Wthout $k$ and $\omega$ you can't add/subtract $x\pm t$. As CuriousMind has commented, it doesn't matter which direction the coordinates axes takes. For these kind of applications there is better suited solution: $$ ...


2

Edit: I think you'll find all the details you need at this question. As Asher commented, when a wave is described as sinusoidal, or triangular, or square, that's its amplitude profile. When a wave is described as plane or spherical, that's the spatial profile perpendicular to the direction of propagation. For example, a plane wave of sinusoidal ...


2

Such a thing is generally possible. You can test this really easy: take a tuning fork without resonator (so really just the fork itself), hit the desk, hold the fork in the air and listen. You will probably hear almost no sound. Now plug your ears, do the same and press the fork root against your forehead. You will see (hear :-) ). Practically, that's a big ...


2

The answer can be found at the sound stackexchange - if you take a pure tone and reverse the phase of one of the stereo channels, there is no "sensible" direction in front of the listener that the sound could come from. We then conclude that the sound comes from behind us (because we have poor ability to figure out the direction of sounds behind us because ...


2

In principle, yes. Sound waves are compressions in a medium, which in principle can be seen if the density contrast between wave crests and troughs is large enough, and the wave speed is small enough. In "everyday object", such as the air, neither of these conditions are fulfilled. But one example of visible sound waves are the so-called baryonic acoustic ...


2

Since this is clearly homework and excercises question, I will provide just hints. This kind of treatment is the same how beats are descripted. Study this article, it will help you get that. Since $k=\frac{\omega}{c}$ where $c$ is constant and the distance is the same for both the signals, it will not cause any more uncertain phase shifts.


1

Sound waves are pressure waves. We measure it as a logarithmic ratio of intensity. Sound intensity is a useful parameter to measure because it's related to the energy incident on a surface which can be easy to measure. Sound intensity is proportional to pressure squared. When calculating decibels we would have to handle that like so: \begin{equation} I = ...


1

Just think about how you might push a child's swing. You apply a push once every oscillation of the swing and thus build up the amplitude of the swing. This is a resonance condition whereas if you pushes the swing at a slightly lower frequency you would not be able to increase the amplitude of the swing as much. Once the swing is at a constant amplitude ...


1

Sound is a longitudinal wave and propagates from the solid into the gas as a longitudinal wave. It is possible to get transverse waves in solids and they are generally known as shear waves. However we would not normally describe a shear wave as a sound wave. Shear waves in a solid will not propagate into a gas. They would simply reflect off the solid gass ...



Only top voted, non community-wiki answers of a minimum length are eligible